Another study, based on data from the Swedish twin registry, shows stress to be a triggering factor for chronic fatigue syndrome (CFS). It also shows that emotional instability is a significant CFS risk factor, although genetic and family factors determine whether this personality trait leads to fatigue.

"Our observations lend support for the hypothesis that CFS represents a disorder of adaptation that is promoted by early environmental insults, leading to failure to compensate in response to challenge," conclude CDC researcher Christine Heim, PhD, and colleagues.

"Stress is a significant risk factor for chronic fatigue-like illness, the effect of which may be buffered by genetic influences," conclude Karolinska Institute researcher Kenji Kato, PhD, and colleagues. "Emotional instability assessed 25 years earlier is associated with chronic fatigue through genetic mechanisms contributing to both personality style and expression of the disorder."

Both studies appear in the November issue of Archives of General Psychiatry.

Worse Trauma, Higher CFS Risk

Heim's CDC team is studying CFS in a community-based sample of more than 56,000 residents of Wichita, Kan. At the time of the study, they had identified 43 people with ongoing CFS. For the study, they compared these people to 60 matched people without fatigue.

A key finding was that more severe childhood trauma was linked to a higher risk of CFS. And the type of childhood trauma was important, too. They found:

Eightfold higher risk of CFS with childhood sexual abuse.

5.9-fold higher risk of CFS with childhood physical neglect.

4.6-fold higher risk of CFS with childhood emotional neglect.

4.3-fold higher risk of CFS with childhood physical abuse.

2.9-fold higher risk of CFS with childhood emotional abuse.

"It appears that CFS is part of a spectrum of disorders that are associated with childhood adversity," Heim and colleagues suggest. "In adulthood, these disorders frequently manifest or worsen in relation to acute stress or challenge. ... These disorders might reflect the brain's inability to adapt or compensate in response to challenge, leading toward maladaptive responses and ultimately disease."

Continued

Stress, Emotional Instability, and CFS

Kato and colleagues looked at data on more than 19,000 twins born in Sweden from 1935 to 1958.

They found that emotionally instability was linked to a 72% higher risk of CFS symptoms. Emotional instability is a personality trait. People with emotional instability tend to have low self-esteem and feelings of anxiety, depression, and guilt.

But emotional instability, Kato and colleagues find, is only part of the equation. High levels of stress -- reported up to 25 years before CFS symptoms appeared -- increased CFS risk by 64%.

When the researchers looked only at twins sharing the same genetic makeup, they found that emotional instability no longer predicted CFS. But stress upped a twin's odds of having CFS by nearly sixfold.

This, Kato and colleagues conclude, means that while emotional instability is an important risk for CFS, whether a person with this personality trait actually gets CFS depends on unknown genetic and family factors. Thus, emotional